149 million years ago, when the Morrison Formation was deposited, the area that is now Dinosaur National Monument looked much different. Large rivers dominated the landscape, flowing from highlands in the south towards the north. A savannah type of environment surrounded the river courses, but instead of a grassland, these savannahs featured ferns and conifers. It was in this environment that dinosaurs like apatasaurus, diplodocus, and stegosaurus grazed while avoiding the predatory allosaurus.